It's the most boring market ever, and that's bullish

The 2015 version of the U.S. stock market has felt like a six-month thrill ride to nowhere.

In fact, by one measure—the amount of time the S&P 500 has spent above or below 3.5 percent from its starting point—this has been the most boring market ever. Another barometer measuring the amount of triple-digit moves by the Dow industrials tells a different story.

Either way, it's been a weirdly volatile yet flat market, and the really strange thing is this: That could set up nicely for a second-half rally.

The S&P 500 has not at any point this year been up or down more than 3.5 percent, a first for the broad market index, according to an analysis from Paul Hickey of Bespoke Investment Group.

With no other years that were as extreme in their movement around level ground, Hickey looked at 10 other points in time when the S&P 500 changed the least in either direction. He found a bullish bias, with the average gain 6.01 percent and the median 5.63 percent. More tellingly, not one of those 10 years saw a market that finished in the red.